The present invention relates to an analog indicator device for timekeepers and the application of the device.
Up to now, chronographs and chronograph watches have been manufactured in various forms that mainly distinguish themselves by the appearance of the control and display elements, the employed materials, their aspect, etc. Generally, these timekeepers comprise a so-called trotteuse or direct-drive seconds-hand that is driven at a period of one turn per minute and may be stopped at will in order to read the measured time. Generally, the dial includes divisions indicating subperiods corresponding to seconds. Fractions of the subperiods can be read with an accuracy of approximately one-fifth of a second if the balance and spring system oscillates at 18,000 vibrations. For optical reasons, a higher reading precision is hardly possible, even in timekeepers having a higher than customary frequency. In certain cases, in addition to the second-hand indicating the number of elapsed seconds, the chronograph comprises counters, e.g. a minute or hour counter, for counting the elapsed minutes or hours.
A device making use of the vernier principle in order to display hours and minutes merely by means of the hour wheel is described in German Patent DE 39 07 873 A. The aim of this device is to reduce the number of indicators, more particularly to omit the minute hand, thereby allowing reduction in the energy consumption of the movement. To this end, the dial includes five areas in the form of concentric circular crowns on each of which eleven equidistant references are arranged, thus obtaining 55 equal circular sectors while each of the references of a given area is offset from the nearest mark of the (two) adjacent area(s) by an angle of 6.5°. An hour wheel in the form of a disk on top of the dial also includes five concentric circular areas on each of which twelve equidistant slots are arranged, thus obtaining 60 equal circular sectors while each of the slots of a given area is offset from the nearest slot of the adjacent area(s) by an angle of 6°. The arrangement of the device allows reading of coincidences separated from each other by 65.45 seconds in the clockwise direction. In order to obtain coincidences separated by 60 seconds, the hour wheel would have to be driven at a period of one turn in eleven hours, thereby falsifying the hour reading.
EP 0 365 443 A2 describes an hour display system composed a moving disk and of a concentric fixed disk, thereby also allowing to read hours and minutes on the hour wheel only. The coincidences are read by juxtaposing the successive marks in the clockwise direction according to the vernier principle. This system requires a counterclockwise numbering of the hour marks on the hour wheel. Furthermore, the user must become familiar with handling and reading a vernier, whereas the hour reading is not only untypical, but first of all difficult and uncomfortable.